Baba Basra 100a - Acquiring the Land by Walking Through it

Hashem said to Avrohom: קום התהלך בארץ לארכה ולרחבה כי לך אתננה. R' Elazar and the Chachamim argue what the purpose was. R' Elazar holds that Avrohom made a kinyan on the land by walking through it, and proves from here that property can be acquired through "hi'luch". The chachamim disagree and hold that without a proper chazaka of improving the property, the land cannot be acquired. So, according to the chachamim the purpose of walking through it must have been כדי שיהא נוח לכבוש לפני בניו.

The Mishneh l'melech in Prashas Derachim (derech hakodesh drush 9) explains that according to R' Elazar, it must be that Avrohom actually made a kinyan on EY at that time and it became his from then. It cannot be that he did a ma'aseh kinyan now for later because חזק וקני לאחר ל' יום לא קנה, a kinyan now doesn't work for later because it is "kal'sa kinyano" - the kinyan ended before it took effect. Based on this, we can explain the machlokes between the shepherds of Avrohom and Lot, to be the machlokes R' Elazar and Chachamim (prashas derachim has a different approach). Lot held like R' Elazar that Avrohom made a proper kinyan which was effective immediately and as rashi (lech li'cha 13:7) explains, realized that he is the inheritor of Avrohom and therefore has the right to graze his sheep in fields of EY. But, Avrohom's shepherds disagreed - why? As rashi explains - והכנעני והפריזי אז יושב בארץ. This can mean simply that they held like the chachamim that Avrohom didn't make an actual kinyan on EY so that Lot's calculation was wrong. Perhaps we can offer another approach, that although technically speaking the shepherds of Lot may be correct (even Avrohom held like R' elazar), that the land belongs to Avrohom already. But, since the nations of kena'an and pri'zi were still "dwelling" in EY, and in their minds the property belonged to them, it would be a chilul Hashem to allow the animals to graze without permission. A halachic disagreement between Avrohom and Lot wouldn't have caused Avrohom to part ways from him, since Lot had halachic justification. The problem was that they agreed from a hashkafa perspective, whether we should behave in a way that makes us look bad in the eyes of others, even when we are technically correct. Just as we are required to be והייתם נקיים מה' ומישראל, we are certainly required to be "clean" in the eyes of the goyim so that we can make a kiddush Hashem, rather than the opposite.

Regarding the peshat in כדי שיהא נוח לכבוש לפני בניו, there are many peshatim. 1. Rashbam - it is a way to symbolize to the satan that EY is ours. Perhaps this can be explained based on rashi in Rosh Hashana 16b, when we show love for mitzvos or EY, it quiets down the satan. 2. Ramban in lech licha explains that it was a ma'aseh avos siman l'banim. It was symbolic of the Jews taking over EY in the future. 3. Based on Rambam and Kesef Mishneh in hilchos bikurim who writes that Avrohom became the av hamon goyim, which means that if all the nations of the world should have an equal claim on EY. Based on this we can explain he had to show ownership over it prior to his name being changed to AvroHOM. 4. It was a psychological acquisition. The purpose was to make the children of Avrohom feel that EY was theirs so that they would be moser nefesh to conquer it in the future.